Increasing efficiency of power generation plants is in progress in response to demands for reduction of carbon dioxide, resource conservation, and the like. Accordingly, increasing temperature of working fluid or the like is actively in progress in gas turbine power generation plants. Various attempts have been made regarding cooling methods of rotor blades, stator blades and the like in accordance with the increasing temperature of the working fluid.
In recent years, power generation plants using carbon dioxide as the working fluid of turbines have been studied. In a power generation plant, carbon dioxide generated in a combustor is circulated as the working fluid in a system. Specifically, the power generation plant includes the combustor which combusts fuel such as hydrocarbon with oxygen. The carbon dioxide introduced to the combustor as the working fluid is introduced to the turbine together with the carbon dioxide and water vapor generated by combustion, and electricity is generated by rotating the turbine.
Turbine exhaust (carbon dioxide and water vapor) exhausted from the turbine is cooled by a heat exchanger, then water is removed to purify the carbon dioxide. This carbon dioxide is compressed to become supercritical fluid by a compressor. A major part of the compressed carbon dioxide is heated by the heat exchanger, to be circulated into the combustor. Out of the compressed carbon dioxide, the carbon dioxide corresponding to a flow rate of the carbon dioxide generated by the combustion of the fuel with the oxygen supplied from external is, for example, recovered or the like, to be utilized for other uses.
The inlet pressure of the turbine when the supercritical carbon dioxide as stated above is used as the working fluid becomes approximately 20 times compared to an inlet pressure of a turbine in a conventional gas turbine. Note that the temperature of the working fluid at the inlet of the turbine exceeds 1000 degrees centigrade, and is equivalent to that of the conventional gas turbine. Accordingly, when the carbon dioxide is used as the working fluid, the heat transfer coefficient at the blade surface of the rotor blade or the like becomes approximately 10 times compared to the conventional gas turbine.